This application provides a data scrambling method, a data descrambling method, and a related device. The method in embodiments of this application includes: first, generating a raw data frame, where the raw data frame includes raw data and a PSB; next, generating a preload pattern of a scrambler based on a target bit, where the target bit is a part of bits in an SFC value corresponding to the raw data frame; and further, scrambling the raw data based on the preload pattern to obtain target data. In this application, the raw data is scrambled, so that bits 0 and bits 1 in the scrambled target data are more evenly distributed. This reduces a possibility that consecutive bits 0 or bits 1 appear in the target data, thereby reducing a bit error rate at a data receiving end.